1. Field of the Invention
This invention relates generally to a seal assembly for sealing rotary equipment utilized primarily in the drying and cooling industry. More particularly, this invention pertains to a segmented seal for sealing the intake and discharge ends of steam tube and direct fire dryers and other types of rotary equipment including coolers which are commonly found in the grain processing and chemical industries.
2. Description of the Prior Art
The grain processing and chemical industries typically have a requirement for removing moisture from raw materials, by-products and finished products. For example, brewers generate vast quantities of "brewers spent grains" which are a high moisture, high protein by-product of the brewing process. This by-product is useful in the cattle feed industry so long as the water is removed prior to feeding livestock. Consequently, cost-effective techniques of removing the moisture from such spent grains has been devised utilizing rotary steam tube dryers. Such dryers are comprised of a rotating cylindrical body having tubes disposed longitudinally therein which are charged with steam to elevate the temperature of the contents of the dryer for removing moisture therefrom by evaporation. Alternatively, the contents of the dryer is heated by direct exposure to a flame. This type of dryer is referred to as a direct fire dryer.
Common to all types of rotary equipment utilized in the grain and chemical industry for drying or cooling is a stationary intake housing for receiving the product. The dried product exits the rotary equipment into a stationary discharge housing. Consequently, prior art means have been devised for sealing the stationary intake and discharge housings with respect to the rotating cylinder so that the product to be dried is not lost or the efficiency of the equipment is not impaired.
Moreover, a pressure gradient often develops from the inside of the equipment with respect to the outside atmosphere. These pressure gradients can be caused by velocity of the product within the equipment as well as by increases in the volume of heated, moisture laden discharge air. These pressure gradients exacerbate the problem of sealing the intake and discharge ends of the equipment as they can cause either undesirable loss of product through the seal, or alternatively result in excessive intake of air which reduces efficiency of the equipment.
Prior art seals are comprised of segmented articulated rings circumferentially disposed about the rotating cylinder and affixed to the stationary housing of rotary equipment. Said arrangement provides axial and radial sealing with respect to the rotating cylinder. However, this prior art apparatus becomes ineffective as the axial and radial sealing surfaces undergo wear. Moreover, although the prior art does allow for limited compensation for irregularities in the roundness of the rotating cylinder, such accommodation is reduced as the prior art apparatus wears with usage.
Additionally, where the rotary equipment relies upon exogenous heat for drying, said equipment undergoes substantial increases in dimension as its temperature becomes elevated. This thermal expansion results in the prior art seal having a maximal effectiveness in a limited temperature range while being less effective at temperatures outside of said range.
Therefore, it is desirable to provide a sealing assembly which accommodates wear along the axial sealing surface of the rotating cylinder as well as accommodates run-out due to irregularities in the roundness of the rotating cylinder's axial sealing surface. Furthermore, it is desirable to provide a seal assembly which operates at maximal efficiency at a wide range of operating temperatures and can accommodate concomitant wide ranging thermal expansion and contraction of the rotary equipment.
Finally, it is desirable to provide a seal assembly which minimizes the leakage of product or atmosphere at the axial and radial sealing surfaces where pressure gradients are likely to exist.